Fatty Liver (cont.)

Jay W. Marks, MD

Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

What are nonalcoholic fatty liver disease and steatohepatitis?

Fatty liver is a condition in which the cells of the liver accumulate abnormally increased amounts of fat. Although excessive consumption of alcohol is a very common cause of fatty liver (alcoholic fatty liver), there is another form of fatty liver, termed nonalcoholic fatty liver disease (NAFLD), in which alcohol has been excluded as a cause. In NAFLD, other recognized causes of fatty liver that are less common causes than alcohol also are excluded.

NAFLD is a manifestation of an abnormality of metabolism within the liver. The liver is an important organ in the metabolism (handling) of fat. The liver makes and exports fat to other parts of the body. It also removes fat from the blood that has been released by other tissues in the body, for example, by fat cells, or absorbed from the food we eat. In NAFLD, the handling of fat by liver cells is disturbed. Increased amounts of fat are removed from the blood and/or are produced by liver cells, and not enough is disposed of or exported by the cells. As a result, fat accumulates in the liver.

NAFLD is classified as either fatty liver (sometimes referred to as isolated fatty liver or IFL) or steatohepatitis (NASH). In both isolated fatty liver and NASH there is an abnormal amount of fat in the liver cells, but, in addition, in NASH there is inflammation within the liver, and, as a result, the liver cells are damaged, they die, and are replaced by scar tissue.

Why is nonalcoholic fatty liver disease important?

NAFLD is important for several reasons. First, it is a common disease, and is increasing in prevalence. Second, NASH is an important cause of serious liver disease, leading to cirrhosis and the complications of cirrhosis--liver failure, gastrointestinal bleeding, and liver cancer. Third, NAFLD is associated with other very common and serious non-liver diseases, perhaps the most important being cardiovascular disease that leads to heart disease and strokes. Fatty liver probably is not the cause of these other diseases, but is a manifestation of an underlying cause that the diseases share. Fatty liver, therefore, is a clue to the presence of these other serious diseases which need to be addressed.